Set the default FieldValuePrinter that is used for all fields that don't have a field-specific printer registered.

Takes ownership of the printer.

void Printer::SetHideUnknownFields( bool hide)

Sets whether we want to hide unknown fields or not.

Usually unknown fields are printed in a generic way that includes the tag number of the field instead of field name. However, sometimes it is useful to be able to print the message without unknown fields (e.g. for the python protobuf version to maintain consistency between its pure python and c++ implementations).